Population Genetics of the Undulate Ray (Raja undulata) in the South Bay of Biscay (Northeast Atlantic)

Rays and skates play pivotal roles in regulating marine ecosystems and are among the most vulnerable groups of marine fish. The undulate skate (Raja undulata) is an elasmobranch species facing intense fishing pressure. To improve management strategies, this study assessed the genetic diversity and structure of R. undulata in the southern Bay of Biscay using mitochondrial DNA (COI) and 12 initially tested microsatellite markers. Genetic analyses of 100 individuals (64 from Asturias and 36 from Galicia, North Spain) revealed low mitochondrial diversity with only two haplotypes detected and significant differentiation between regions (ΦST =0.23, p<0.05). Microsatellite data (9 loci) revealed moderate genetic diversity (Ho=0.68) and low but significant FST values between regions (FST=0.002, p< 0.05). However, this pattern was not consistent when using AMOVA (p=0.052), suggesting some level of connectivity. The data showed no signs of recent population bottlenecks or demographic expansions. The different patterns observed between markers may indicate male-biased dispersal. Our data reject panmixia and indicate caution since local populations may be particularly vulnerable to anthropogenic pressures despite signs of recovery. Our results highlight the importance of filling gaps in genetic and ecological data to inform adaptive conservation strategies in the southern Bay of Biscay